Most electronic equipment is manufactured to operate on an AC voltage, usually either 115 volts AC or 230 volts AC. If it is desired to operate electronic equipment from a power source having a voltage level other than the level at which the device is intended to operate, it has heretofore been necessary to use an external step-down/step-up transformer accessory. Many equipments are designed to operate from either 115 volts AC or 230 volts AC but an operator must set a mechanical switch in the correct position. If the switch is not set for the proper voltage level, there can, of course, be damage to the equipment.
Some electronic equipments are manufactured to operate on DC voltages, usually either 12 volts DC or 24 volts DC. For example, electronic equipments intended for use in land, mobile, or maritime operation in small vessels are usually designed to operate on a DC voltage. The voltage available at most repair facilities is, however, an AC voltage, usually 115 volts AC or 230 volts AC. In order to repair and test such DC equipment, it has heretofore been necessary to have a separate DC power supply for converting a AC source voltage to the required DC voltage.